骨髓增生异常综合征的常见染色体核型异常有（）
A.-5/5q-
B.-7/7q-
C.+8
D.20q-
E.-14
参考答案：A, B, C, D
小华上午7：30去学校，路上要走10分钟，她（ ）到校。
When navigating using DGPS（Differential Global Positioning System）you may expect your position to be accurate to within a radius of（）.
A.10 meters
B.20 meters
C.50 meters
D.100 meters
